—Because of shrinking structure sizes and operating voltages, computing hardware exhibits an increasing susceptibility against transient hardware faults: Issues previously only known from avionics systems, such as bit flips caused by cosmic radiation, nowadays also affect automotive and other cost-sensitive “ground-level” control systems. For such cost-sensitive systems, many software-based measures have been suggested to harden applications against transient effects. However, all these measures assume that the underlying operating system works reliably in all cases. We present software-based concepts for constructing an operating system that provides a reliable computing base even on unreliable hardware. Our design is based on two pillars: First, strict fault avoidance by static tailoring and elimination of susceptible indirections. Second, reliable fault detection by finegrained arithmetic encoding of the complete kernel execution path. Compared to an industry-grade off-the-s...